Portable sensor

ABSTRACT

A vapor sensing device that is sufficiently small and lightweight to be handheld, and also modular so as to allow the device to be conveniently adapted for use in sensing the presence and concentration of a wide variety of specified vapors. The device provides these benefits using a sensor module that incorporates a sample chamber and a plurality of sensors located on a chip releasably carried within or adjacent to the sample chamber. Optionally, the sensor module can be configured to be releasably plugged into a receptacle formed in the device. Vapors are directed to pass through the sample chamber, whereupon the sensors provide a distinct combination of electrical signals in response to each. The sensors of the sensor module can take the form of chemically sensitive resistors having resistances that vary according to the identity and concentration of an adjacent vapor. These chemically sensitive resistors can each be connected in series with a reference resistor, between a reference voltage and ground, such that an analog signal is established for each chemically sensitive resistor. The resulting analog signals are supplied to an analog-to-digital converter, to produce corresponding digital signals. These digital signals are appropriately analyzed for vapor identification.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional application of U.S. Application Ser.No. 09/796,877, filed Feb. 28, 2001, allowed to be grated on Jul. 16,2002 now U.S. Pat. No. 6,418,783 which is a continuation of U.S.Application Ser. No. 09/548,948, filed Apr. 13, 2000, now U.S. Pat. No.6,234,006, dated May 22, 2001, which is a continuation application ofU.S. Application Ser. No. 09/271,873, filed Mar. 18, 1999, now U.S. Pat.No. 6,085,576, dated Jul. 11, 2000, which application is acontinuation-in-part of U.S. patent application Ser. No. 09/178,443,filed Oct. 23, 1998, now abandoned which is a continuation-in-part ofU.S. patent application Ser. No. 09/045,237, filed Mar. 20, 1998 nowabandoned. U.S. application Ser. No. 09/271,873 is also acontinuation-in-part of U.S. patent application Ser. No. 09/141,847,filed Aug. 27, 1998 now abandoned. U.S. application Ser. No. 09/271,873further claims the benefit of U.S. Provisional Application Serial No.60/122,688, filed Mar. 3, 1999. All of these applications areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to the detection and identification ofanalytes using a portable sensing apparatus. More particularly, thepresent invention relates to a portable handheld electronic nose(e-nose) device.

An electronic nose is an instrument used to detect vapors or chemicalanalytes in gases, solutions, and solids. In certain instances, theelectronic nose is used to simulate a mammalian olfactory system. Ingeneral, an electronic nose is a system having an array of sensors thatare used in conjunction with pattern-recognition algorithms. Using thecombination of chemical sensors, which produce a fingerprint of thevapor or gas, the recognition algorithms can identify and/or quantifythe analytes of interest. The electronic nose is thus capable ofrecognizing unknown chemical analytes, odors, and vapors.

In practice, an electronic nose is presented with a substance such as anodor or vapor, and the sensor converts the input of the substance into aresponse, such as an electrical response. The response is then comparedto known responses that have been stored previously. By comparing theunique chemical signature of an unknown substance to “signatures” ofknown substances, the unknown analyte can be determined. A variety ofsensors can be used in electronic noses that respond to various classesof gases and odors.

A wide variety of commercial applications are available for electronicnoses including, but not limited to, environmental toxicology andremediation, biomedicine, such as microorganism classification ordetection, material quality control, food and agricultural productsmonitoring, heavy industrial manufacturing, ambient air monitoring,worker protection, emissions control, and product quality testing. Manyof these applications require a portable device because they are locatedin the field or because they have an inaccessible location for largerlaboratory models. Conventionally, most of the electronic noses havebeen large cumbersome laboratory models incapable of being used in thefield and pilot plant applications. If available, a portable or handhelddevice would provide the portability required for pilot plant and fieldlocations. Unfortunately, the portable chemical detectors that have beendeveloped thus far have many limitations that have kept them from beingwidely accepted.

For instance, U.S. Pat. No. 5,356,594, which issued to Neel et al.,discloses a portable volatile organic monitoring system designed for usein detecting fugitive emissions. The device includes a bar code readerfor inventorying the emission site. The device contains a single sensorresponsive to ionized gas, however the device only detects the amount(i.e., concentration) of the volatile compound. The device is incapableof identifying the volatile organic compound. Thus, the device is merelya vapor amount logger and not a portable electronic nose. As such, theuser is required to know the identity of the vapor being quantitated orthis information must be stored elsewhere.

Another example of a portable device is disclosed in U.S. Pat. No.4,818,348 issued to Stetter. Although this portable device is moresophisticated than the previous example, it still has many limitations.In this instance, the device is capable of identifying a gas or vapor,but the applications are quite limited because of sensor architecturallimitations. The sensors making up the array are permanently fixed, andthus, the number and variety of analytes and gases that the device iscapable of identifying is quite small. Moreover, because the analyte orvapor being identified interacts with each sensor of the array in adifferent amount, the reproducibility and stability of the device isquite limited. These limitations effect the device's accuracy inidentifying unknowns.

In view of the foregoing, there remains a need in the art for anelectronic nose that is portable and, in certain instances, handheld.Moreover, a device is needed that is useful in a broad variety ofapplications and can respond accurately to a broad variety of gases,analytes, and fluids. A vapor-sensing device is needed that is veryversatile, stable, and meets the needs of a wide range of industries andusers. The present invention fulfills these and other needs.

SUMMARY OF THE INVENTION

The invention relates generally to a sensing apparatus (also referred toas an electronic-nose or e-nose device). The apparatus is compact and,in certain embodiments, configured to be a handheld device. The e-nosedevice can be used to measure or identify one or more analytes in amedium such as vapor, liquid, gas, solid, and others. Some embodimentsof the e-nose device includes at least two sensors (i.e., an array ofsensors) and, in some other embodiments, about two to about 200 sensorsin an array and preferably about four to about 50 sensors in the array.

The e-nose device is versatile and meets the needs of a wide range ofapplications in various industries. In certain embodiments, the deviceis designed as a slim handheld, portable device with variousfunctionalities. In another embodiments, the device is designed as aportable field tool with full functionality. The e-nose device typicallyincludes an internal processor for processing samples and reportingdata. Optionally, the device can be coupled to a computer, such as apersonal computer, for access to set-up and advanced features and fortransfer of data files.

In some embodiments, sections of the e-nose device are disposed withinmodules that can be installed, swapped, and replaced as necessary. Forexample, the sensor module, sampling wand or nose, battery pack, filter,electronics, and other components, can be modularized, as describedbelow. This modular design increases utility, enhances performance,reduces cost, and provides additional flexibility and other benefits.

A specific embodiment of the invention provides a handheld sensingapparatus that includes a housing, a sensor module, a sample chamber,and an analyzer. The sensor module and the analyzer mount in thehousing. The sensor module includes at least two sensors that provide adistinct response to a particular test sample. The sample chamber isdefined by the housing or the sensor module, or both, and incorporatesan inlet port and an outlet port. The sensors are located within oradjacent to the sample chamber. The analyzer is configured to analyze aparticular response from the sensors and to identify or quantify, basedon the particular response, analytes within the test sample.

In a variation of the above embodiment, the housing of the handheldsensing apparatus includes a receptacle, and the sensor module isremovably mounted in the receptacle of the housing. In this embodiment,the sensor module can include one or more sensors.

Another specific embodiment of the invention provides a sensor moduleconfigured for use with a sensing apparatus. The sensor module isdisposed within a housing that defines a receptacle. The sensor moduleincludes a casing, a sample chamber, an inlet port, an outlet port, atleast two sensors, and an electrical connector. The casing is sized andconfigured to be received in the receptacle of the sensing apparatus.The inlet port is configured to be releasably engageable with a portconnection of the sensing apparatus when the sensor module is receivedin the receptacle. The inlet port receives a test sample from thesensing apparatus and directs the test sample to the sample chamber. Theoutlet port is configured to discharge the test sample from the samplechamber. The sensors are located within or adjacent to the samplechamber and are configured to provide a distinct response when exposedto one or more analytes located within the sample chamber. Theelectrical connector is configured to be releasably engageable with amating electrical connector of the sensing apparatus when the sensormodule is received in the receptacle. The electrical connector transmitsthe characteristic signals from the sensors to the sensing apparatus.

Yet another specific embodiment of the invention provides a handheldsensing apparatus for measuring the concentration of one or moreanalytes within a sample chamber. The sensing apparatus includes two ormore chemically sensitive resistors, conditioning circuitry, ananalog-to-digital converter (ADC), and an analyzer. Each chemicallysensitive resistor has a resistance that varies according to aconcentration of one or more analytes within the sample chamber. Theconditioning circuitry couples to the chemically sensitive resistors andgenerates an analog signal indicative of the resistance of theresistors. The ADC couples to the conditioning circuitry and provides adigital signal in response to the analog signal. The analyzer couples tothe ADC and determines, based on the digital signal, the identity orconcentration of the analyte(s) within the sample chamber.

Yet another embodiment of the invention provides a portable, handheldvapor sensing apparatus that includes a sensor module incorporating aplug-in array of vapor sensors that provide different electricalresponses to one or more distinct vapors. The apparatus includes ahandheld housing, and the sensor module optionally can be removablymounted in a receptacle formed in the housing. The sensor module definesa sample chamber to which the array of vapor sensors is exposed. Thesample chamber incorporates a vapor inlet and a vapor outlet, and a pumpis mounted within the housing for directing a vapor sample from thevapor inlet through the sample chamber to the vapor outlet. A monitoringdevice also is mounted within the housing, for monitoring the electricalresponses of the array of vapor sensors and for producing acorresponding plurality of sensor signals. In addition, an analyzer ismounted within the housing for analyzing the plurality of sensor signalsand to identify any vapor sample directed through the sample chamber bythe pump.

In more detailed features of the invention, the handheld vapor sensingapparatus further includes a controller or processor configured tocontrol the pump either to direct one of a plurality of reference vaporsor an unknown vapor sample through the sample chamber. When thecontroller is controlling the pump to direct one of the plurality ofreference vapors through the sample chamber, the monitoring devicemonitors the electrical responses of the array of vapor sensors toproduce a reference signature. Thereafter, when the controller iscontrolling the pump to direct the unknown vapor sample through thesample chamber, the monitoring device monitors the electrical responsesof the array of vapor sensors to produce a vapor sample signature. Theanalyzer then compares the vapor sample signature with a plurality ofreference signatures, to identify the unknown vapor sample.

In other more detailed features of the invention, the sample chamber ofthe handheld vapor sensing apparatus is defined by the sensor module,alone, and it is sealed from the external environment except for thevapor inlet and the vapor outlet. In addition, each sensor moduleincludes a plurality of first electrical connectors and a plurality ofdevices of substantially identical size and shape, the devices togethercarrying the array of vapor sensors and each including a secondelectrical connector along one edge thereof, for mating engagement withone of the first electrical connectors.

In yet further more detailed features of the invention, the handheldvapor sensing apparatus further includes an electrical circuit thatcontrols the temperature of the array of vapor sensors. In addition,when the sensor module is configured to be removably mounted in thehousing receptacle, the module carries an identifier for identifying thevapor sensors it carries, and the monitor further is configured to readthe identifier carried by the sensor module received in the receptacle.

In an embodiment, the sensors are implemented with chemically sensitiveresistors having resistances that vary according to the concentration ofone or more prescribed vapors within the sample chamber. Thesechemically sensitive resistors are each connected in series with aseparate reference resistor, between a reference voltage and ground,such that an analog signal is established for each chemically sensitiveresistor. An analog-to-digital converter is responsive to these analogsignals and to the reference voltage, to produce digital output signalsindicative of the resistances of the various chemically sensitiveresistors. A multiplexer can be included for sequentially connecting thevarious analog output signals to the analog-to-digital converter. Inaddition, an analyzer is responsive to the digital output signals, todetermine the presence and/or concentration of one or more prescribedvapors within the sample chamber.

Other features and advantages of the present invention should becomeapparent from the following description of the preferred embodiments,taken in conjunction with the accompanying drawings, which illustrate,by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a pictorial view of an operator using an e-nose device ofthe invention.

FIGS. 2A and 2B show a top and bottom perspective view, respectively, ofan embodiment of an e-nose device.

FIGS. 3A-1-3A-7 show six perspective views of an embodiment of anothere-nose device. FIG. 3A-1 and 3A-2 show a top view respectively; FIG.3A-3 shows a front view; FIG. 3A-4 shows a side view; FIG. 3A-5 shows aback view; FIG. 3A-6 shows a side view; and FIG. 3A-7 shows a bottomview

FIG. 3B shows four different embodiments of noses for the e-nose deviceof FIG. 3A.

FIG. 4 shows a diagram of an embodiment of the subsystems of the e-nosedevice.

FIG. 5 shows an exploded perspective view of some of the majorcomponents of the e-nose device of FIG. 2A.

FIGS. 6A and 6B show an exploded perspective view of two embodiments ofthe mechanical subsystem of the e-nose device.

FIG. 6C shows an exploded perspective view of an embodiment of a filter.

FIGS. 7A-7B show a perspective view and a top sectional view,respectively, of an embodiment of a sensor module that includes foursensor devices mounted within two sample chambers.

FIG. 7C shows a perspective view of the sensor array device.

FIGS. 8A and 8B show a perspective view and a top sectional view,respectively, of an embodiment of another sensor module that includesfour plug-in sensor devices within a single sample chamber.

FIGS. 9A through 9C show a perspective view, a side sectional view, anda partial top sectional view, respectively, of an embodiment of a yetanother sensor module that includes a single sensor array device.

FIG. 10 shows various accessories for the e-nose device

FIG. 11 shows a perspective view of an e-nose device shown mountedvertically in an electrical charging station and coupled to a hostcomputer.

FIG. 12A shows a diagram of an embodiment of the electrical circuitrywithin the e-nose device.

FIG. 12B shows an embodiment of a voltage divider network used tomeasure the resistance of a chemically sensitive resistor.

FIG. 12C shows a diagram of another embodiment of the electricalcircuitry within the e-nose device.

FIGS. 13A through 13G show an embodiment of suitable flowcharts of thefunctional steps performed by the e-nose device in implementing themeasurement and analysis procedures.

FIG. 14 shows a diagram of an embodiment of the menu selection for thee-nose device.

FIG. 15 shows a graph of a principal component analysis of the responsesto a series of esters using the handheld apparatus of the presentinvention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

FIG. 1 shows a pictorial view of an operator using an e-nose device 100of the invention. In the embodiment shown in FIG. 1, e-nose device 100is a portable, handheld instrument for sensing the presence of one ormore specified analytes in a particular sample. As use herein, a sampleis a unit of a vapor, liquid, solution, gas, solid, or other forms, andmixtures thereof, of a substance being analyzed. Thus, a sample includeschemical analytes, odors, vapors, and others. The sample can comprise asingle analyte or a plurality of analytes. In FIG. 1, e-nose device 100is used for industrial monitoring and detection, i.e., to identity andquantify noxious gas escaping from an industrial valve assembly. E-nosedevice 100 can also be used for many other applications, as enumeratedbelow.

FIG. 2A shows a top perspective view of an embodiment of an e-nosedevice 100 a. E-nose device 100 a includes an elongated housing 110 ahaving a lower end sized to be conveniently grasped and supported by thehand of an operator. A display 120 a and several push-button controlswitches 122 a through 122 c are located on the housing's topside, forconvenient viewing and access by the operator. Push-button switches 122are used to control the device during its various operating modes.Display 120 a displays information about such operating modes and theresults of the device's sensing.

A tubular sampling wand 130 a and an exhaust port 134 are provided torespectively receive and discharge samples to be analyzed. The samplingwand is also referred to as a nose or snout. A plug-in sensor module 150a is shown installed in its socket located at the base of e-nose device100 a. The operation of sensor module 150 a is described in detailbelow. An electrical connector 126 located at the lower end of housing110 a allows for communication with a host computer, and electricalcontacts 128 allow for application of external power that could be usedto operate the e-nose device and to recharge the rechargeable batterywithin the e-nose device.

FIG. 2B shows a bottom perspective view of e-nose device 100 a. As shownin FIG. 2B, one sampling wand 130 a 1 is secured in place and a secondsampling wand 130 a 2 is being stored in an elongated recess 162 locatedon the underside of device 100 a. Sampling wand 130 a can be stored whennot in use and is releasably secured in place by a pair of spring clips164 a and 164 b. Plug-in sensor module 150 a is shown removed from itssocket 152.

FIGS. 3A-1-3A-7 show six perspective views of an embodiment of anothere-nose device 100 b. E-nose device 100 b includes a nose 130 b, adisplay 120 b, and a set of buttons 124. Similar to e-nose device 100 a,nose 130 b in e-nose device 100 b is removably coupled to a housing 110b. A set of connectors 127 allows for interconnection with externaldevices and systems.

FIG. 3B shows four different embodiments of noses 130 c through 130 f.As these examples illustrate, the noses can be specially dimensioned forimproved performance in specific applications.

FIG. 4 shows a diagram of an embodiment of the subsystems of e-nosedevice 100. The upper half of FIG. 4 shows an electrical subsystem 410and the lower half shows a (i.e., substantially mechanical) subsystem412 that processes test samples. Within subsystem 412, a test sample isreceived via a nose 430 and provided to a manifold 440. Similarly, areference or background sample is received via an intake port 432 andprovided through a filter 436 to manifold 440. Filter 436 can be a blankfilter, a carbon filter, or others. Manifold 440 directs the test andclean samples to a solenoid 444 that selects one of the samples as thesolenoid output. The selected sample is directed through manifold 440 toa sensor module 450. Sensor module 450 includes at least two sensorsthat detect analytes in the selected sample. Sensor module 450 generatesa signal (or a “signature”) indicative of the detected analytes andprovides this signal to electrical subsystem 410. The selected sample isthen provided from sensor module 450, through manifold 440, furtherthrough a pump 460, and to an exhaust port 434. Nose 430, intake port432, exhaust port 434, and sensor module 450 in FIG. 4 generallycorresponds to nose 130 a, intake port 132, exhaust port 134, and sensormodule 150 a in FIG. 2A, respectively.

FIG. 4 shows an embodiment of subsystem 412. Many other components anddevices (not shown) can also be included in subsystem 412. Further, itis not necessary for all of the components and devices shown in FIG. 4to be present to practice the present invention. Moreover, thecomponents and devices may be arranged in different configurations thanthat shown in FIG. 4. For example, pump 460 can be coupled to the outputof solenoid 444 instead of exhaust port 434.

As shown by the embodiment in FIG. 4, electrical subsystem 410 includesa PCB assembly 470 that interconnects with a display 472, a battery pack474, a keypad 476, an analog port 478, an interface 480, and switches482 a and 482 b. Display 474 can be a liquid crystal display (LCD) andcan include backlight controllers drivers and (optionally) a touchpad. Acontrast adjustment mechanism can be provided to adjust display 472.Electrical subsystem 410 is described in further detail below.

FIG. 5 shows an exploded perspective view of some of the majorcomponents of e-nose device 100 a. FIG. 5 also depicts an embodiment ofa subsystem 412 a. In use, e-nose device 100 a is configured to draw ina test sample (i.e., in a vapor, liquid, or gas medium) from a locationof interest (i.e., the space adjacent to the valve assembly in FIG. 1)through sampling wand 130 a, and to direct this sample through plug-insensor module 150 a installed in socket 152. After passing throughsensor module 150 a, via ports 512 a and 512 b, the sample is directedoutwardly through exhaust port 134 at the side of the device. Atspecified times during the device's various operating modes, a referencesample is drawn into the device via intake port 132, directed throughsensor module 150 a, and discharged through exhaust port 134.

The device's housing 110 a can be formed of molded plastic and includesa lower half 112 a and an upper half 112 b. Many of the device'sinternal components are conveniently and efficiently mounted on aprinted circuit board (PCB) 510 that extends substantially across thedevice's interior volume. Display 120 a is mounted at the top end of thePCB, where it is visible through an aperture 520 formed in the housing'supper half 112 a. The push-button control switches 122 a through 122 care mounted below display 120 a, in positions where they can extendthrough correspondingly sized openings 522 formed in the housing's upperhalf 112 a.

A valve assembly 540 mounted on the underside of PCB 510 receives thetest sample drawn into e-nose device 100 a via sampling wand 130 a andthe reference sample via intake port 132. The test sample is directedfrom sampling wand 130 a to the valve assembly via a tube 532, and theclean sample is directed from intake port 132 to the valve assembly viaa tube 534. Valve assembly 540 is configured to select from one of twosources, coming via either sampling wand 130 a or intake port 132. Fromvalve assembly 540, the sample from the selected source is directed viaa tube 536 through socket 152 to sensor module 150 a, which is locatedon the top side of the PCB. After analysis by the sensor module, thesample is directed through a tube 538 to a pump 560 located on theunderside of the PCB. Finally, the sample is discharged from the deviceby directing it from pump 560 through a tube 562 to exhaust port 134.Alternatively, pump 560 could be located in the path between valveassembly 540 and sensor module 150 a. In an embodiment, the componentscoming in contact with the sample being processed (including tubes 532,534, 536, 538, and 562) are formed of an inert or non-corrosivematerial, such as Teflon, stainless steel, or Teflon-coated metal. Valveassembly 540 in FIG. 5A generally corresponds to manifold 440 andsolenoid 444 in FIG. 4, and pump 560 corresponds to pump 460.

In certain aspects, the handheld apparatus of the present inventionincludes an optional preconcentrator. Advantageously, with certainanalytes, such as high vapor pressure analytes, the analyte isconcentrated on an absorbent. The preconcentrator can be used toincrease the concentration of analytes in the test sample.Preconcentrators are traps composed of an adsorbent material. In use, anadsorbent material attracts molecules from the gas sample that areconcentrated on the surface of the adsorbent. Subsequently, the sampleis “desorbed” and analyzed. Suitable preconcentrator materials include,but are not limited to, a polymeric adsorbent material, unsilanizedglass wool, Teflon or porus glass fiber, and the like. The adsorbentmaterial is packed in a tube, such as a steel tube.

During use, the sample is drawn into the trap that concentrates thecomponents of interest. In some instances, the tube is wrapped with awire through which current can be applied to heat and thus, desorb thetest sample. The sample is thereafter transferred into the modulecontaining the sensors.

The preconcentrator can be disposed in various locations between thesampling wand and the sensor module. In certain aspects, thepreconcentrator can be placed in the nozzle of the device or,alternatively, in the manifold or other convenient location upstream ofthe sensor module. For example, the preconcentrator can be disposedwithin valve assembly 540, or housed in a unit coupled to the valveassembly (not shown in FIG. 5). Optionally, additional valves can beinstalled in the device facilitating preconcentration and sensing.

Suitable commercially available adsorbent materials used inpreconcentrators include, but are not limited to, Tenax TA, Tenax GR,Carbotrap, Carbopack B and C, Carbotrap C, Carboxen, Carbosieve SIII,Porapak, Spherocarb, and combinations thereof. Preferred adsorbentcombinations include, but are not limited to, Tenax GR and Carbopack B;Carbopack B and Carbosieve SIII; and Carbopack C and Carbopack B andCarbosieve SIII or Carboxen 1000. Those skilled in the art will know ofother suitable absorbents.

Operation of e-nose device 100 is controlled by a processor disposedwithin an electronic unit 570 mounted on the topside of PCB 510.Electronic unit 570 further includes one or more memory devices to storeprogram codes, data, and other configuration information. The electronicunit and control of the e-nose device is described in further detailbelow.

FIG. 6A shows an exploded perspective view of an embodiment of anothersubsystem 412 b. Subsystem 412 b includes a manifold 640 a mounted on amanifold seal plate 642 a. Manifold 640 a includes fittings for mountinga valve (or solenoid) 644 a, fittings for mounting a sensor module 650a, and fittings for mounting a pump 660 a The sample is directed betweenthe various sub-assemblies (e.g., valve 644 a, sensor module 650 a, andpump 660 a) via cavities located within manifold 640 a and tubes (notshown). Manifold 640 a further includes a recessed opening 648 aconfigured to receive a filter 636 a.

FIG. 6B shows an exploded perspective view of an embodiment of yetanother subsystem 412 c. Subsystem 412 c includes a manifold 640 bmounted on a manifold seal plate 642 b via a seal plate gasket 644 b.Manifold 640 b includes fittings for mounting a valve (or solenoid) 644b and fittings for mounting a pump 660 b. A filter cartridge 646 bmounts on top of manifold 640 b and includes a recessed opening 648 bconfigured to receive a filter element. A filter cover 636 b enclosesrecessed opening 648 b and an O-ring 638 b provides a seal for thefilter. The sample is directed between the various sub-assemblies (e.g.,valve 644 b and pump 660 b) via cavities located within manifold 640 band tubes (not shown).

Filter 636, manifold 640, valve 644, sensor module 650, and pump 660 inFIGS. 6A and 6B correspond to filter 436, manifold 440, solenoid 444,sensor module 450, and pump 460 in FIG. 4, respectively.

FIG. 6C shows an exploded perspective view of an embodiment of a filter.The filter includes a circular base unit 680 having an outer wall 682and an inner wall 686. A set of small-size openings is disposed withinouter wall 682 for drawing in samples into the filter. A inner circularring 684 covers inner wall 686 that has disposed therein another set ofsmall size openings, for drawing the samples from the filter. A filtermaterial (e.g., charcoal) 688 for filtering the samples is disposedwithin the space between the outer and inner walls. O-ring 638 b is usedto seal the filter.

FIGS. 7A-7B show a perspective view and a top sectional view,respectively, of an embodiment of a sensor module 150 b that includesfour sensor devices mounted within two sample chambers 710 a and 710 b.In FIGS. 7A and 7B, sensor module 150 b is depicted as being configuredfor non-removable securement to the PCB, but which alternatively couldbe configured as a plug-in module such as sensor module 150 a. In aspecific embodiment, sensor module 150 b incorporates four plug-insensor array devices 720, each including eight chemically sensitivesensors 740. Sensor module 150 b can include greater or fewer number ofsensor array devices, and each sensor array device can include greateror fewer number of sensors. The four sensor array devices 720 aremounted vertically in pairs on a board 730. A cover 732 having a pair ofelongated recesses is secured over board 730 so as to define twoseparate sample chambers 710 a and 710 b, one for each pair of sensorarray devices 720. Sensor array devices 720 are of similar shape andsize, and each can be received in any one of the four connectors, orreceptacles 722, formed in board 730.

FIG. 7C is a perspective view of one sensor array device 720. In anembodiment, each sensor array device 720 includes an array of eightchemically sensitive sensors 740, each providing a particularcharacteristic response when exposed to a test sample carrying analytesto be sensed. In an embodiment, the sensors are implemented usingchemically sensitive resistors that provide particular resistances whenexposed to a test sample. A multi-contact electrical connector 742 islocated along the lower edge of sensor array device 720 and isconfigured for insertion into one of four receptacles 722. Suitablesensor arrays of this kind are disclosed in U.S. Pat. No. 5,571,401,issued in the names of Nathan S. Lewis et al., entitled “Sensor Arraysfor Detecting Analytes in Fluids,” and incorporated herein by reference.Those of ordinary skill in the art will appreciate that variousalternative chemically sensitive sensors or devices could also be used.

As shown in FIG. 7B, the test sample is directed through sensor module150 b from an inlet port 750, through two sample chambers 710 a and 710b, and to an outlet port 760. Sensor array devices 720 are arranged suchthat the test sample moves laterally across the exposed chemicallysensitive sensors. Baffles 762 and 764 are located at the respectiveleading and trailing ends of each sample chamber, to assist in providingan efficient flow pattern, as shown in FIG. 7B.

FIGS. 8A and 8B show a perspective view and a top sectional view,respectively, of an embodiment of another sensor module 150 c thatincludes four plug-in sensor devices 820 within a single cavity orsample chamber 810. Sample chamber 810 is defined, in part, by a cover832 that is secured over a board 830. This configuration can be designedto provide a longer dwell time for the test sample within the samplechamber, which can be advantageous in some applications.

Like the chemically sensitive sensors included on sensor array devices720 in FIGS. 7A and 7B, the chemically sensitive sensors included onsensor array device 820 in FIGS. 8A and 8B can take the form of thearrays disclosed in U.S. Pat. No. 5,571,401. Those of ordinary skill inthe art will appreciate that various alternative chemically sensitivesensors or devices could also be used.

FIGS. 9A and 9B show a perspective view and a side sectional view,respectively, of an embodiment of yet another sensor module 150 d thatincludes a single sensor array device 920. In a specific embodiment,sensor array device 920 includes 32 chemically sensitive sensorsarranged in a two-dimensional grid and is mounted in a generallyhorizontal orientation on a socket 922. Of course, sensor array device920 can include greater or fewer number of sensors. A screen 924 (seeFIGS. 9B and 9C) overlays sensor array device 920 and, in an embodiment,includes a separate opening 926 overlaying each chemically sensitivesensor. Screen 924 is attached to a cover 932, the combination of whichdefines an upper chamber 934 and a lower chamber 936. As shown in FIG.9B, the test sample being analyzed is directed from an inlet port 950 toupper chamber 934, and from there through screen 924 to lower chamber936 where it passes across the chemically sensitive sensors. The testsample then exits through an outlet port 960. Again, it will beappreciated that various alternative chemically sensitive sensors anddevices could also be used.

The e-nose device of the invention includes an array of sensors and, incertain instances, the sensors as described in U.S. Pat. No. 5,571,401are used. Various sensors suitable for detection of analytes include,but are not limited to: surface acoustic wave (SAW) sensors; quartzmicrobalance sensors; conductive composites; chemiresitors; metal oxidegas sensors, such as tin oxide gas sensors; organic gas sensors; metaloxide field effect transistor (MOSFET); piezoelectric devices; infraredsensors; sintered metal oxide sensors; Pd-gate MOSFET; metal FETstructures; metal oxide sensors, such as a Tuguchi gas sensors;phthalocyanine sensors; electrochemical cells; conducting polymersensors; catalytic gas sensors; organic semiconducting gas sensors;solid electrolyte gas sensors; piezoelectric quartz crystal sensors; andLangmuir-Blodgett film sensors.

In a preferred embodiment, the sensors of the present invention aredisclosed in U.S. Pat. No. 5,571,401, incorporated herein by reference.Briefly, the sensors described therein are conducting materials andnonconducting materials arranged in a matrix of conducting andnonconducting regions. The nonconductive material can be a nonconductingpolymer such as polystyrene. The conductive material can be a conductingpolymer, carbon black, an inorganic conductor and the like. The sensorarrays comprise at least two sensors, typically about 32 sensors, and incertain instances 1000 sensors. The array of sensors can be formed on anintegrated circuit using semiconductor technology methods, an example ofwhich is disclosed in PCT Patent Application Serial No. WO99/08105,entitled “Techniques and Systems for Analyte Detection,” published Feb.19, 1999, and incorporate herein by reference.

In certain instances, the handheld device of the present inventioncomprises an array of surface acoustic wave (SAW) sensors, preferablypolymer-coated SAW sensors. The SAW device contains up to six andtypically about four sensors in the array. Optionally, the deviceincludes a preconcentrator with a heater for desorption of the sample.

As will be apparent to those of skill in the art, the sensors making upthe array of the present invention can be made up of various sensortypes as set forth above. For instance, the sensor array can comprise aconducting/nonconducting regions sensor, a SAW sensor, a metal oxide gassensor, a conducting polymer sensor, a Langmuir-Blodgett film sensor,and combinations thereof.

FIG. 10 shows various accessories for the e-nose device. A case 1010 isprovided for easy transport of the e-nose device and its accessories. Apower cord 1012 and a car cord 1014 can each interconnects the e-nosedevice to a power source (i.e., a wall socket or car lighter) forrecharging a rechargeable battery within the e-nose device. These cordsalso allow for operation of the e-nose device without the battery.. Abracket or stand 1016 holds the e-nose device in the desired position. A(primary or spare) battery 1018 allows the e-nose device to be usedwithout connection to a power source. A serial cable 1020 and an analogcable 1022 are used to interconnect the e-nose device with a personalcomputer and other test equipment. A stylus 1024 is provided for usewith a touchscreen. One or more snouts 1030 can also be provided asspares or for use in a particular set of applications. A sample syringe1032 can be used for collection of test samples.

FIG. 11 is a perspective view of e-nose device 100 shown mountedvertically in an electrical charging station 1108 and coupled to a hostcomputer 1110. Charging station 1108 recharges the rechargeable batteryof e-nose device 100 via electrical contacts 128 (see FIGS. 2A and 2B).E-nose device 100 is also depicted being coupled to host computer 1110via a data line 1120. Host computer 1110 can be used to update e-nosedevice 100 with various information such as the identity of varioustarget vapors to which the device is to be exposed, as well as toretrieve information from the device such as the results of the device'ssample analyses.

FIG. 12A is a diagram of an embodiment of the electrical circuitrywithin e-nose device 100. In an embodiment, the electrical circuitrymeasures the resistances of the arrays of chemically sensitive resistorsmounted on the sensor array devices (see FIGS. 7 through 9) andprocesses those measurements to identify and quantify the test sample.The circuitry is mounted, in part, on the PCB and includes a processor1210, a volatile memory (designated as a RAM) 1212, a non-volatilememory (designated as ROM) 1214, and a clock circuit 1216. In theembodiment in which plug-in sensor module 150 a is used (see FIGS. 2Aand 5), the chemically sensitive resistors are coupled to the electricalcircuitry via mating electrical connectors 552 a and 552 b (see FIG. 5)that are engaged when sensor module 150 a is plugged into e-nose device100 a.

The chemically sensitive resistors used to implement the sensorstypically have baseline resistance values of greater than 1 kilo-ohm(KΩ). These baseline values can vary as much as ±50% over time. Forexample, a particular chemically sensitive resistor may have a baselineresistance that varies between 15 KΩ and 45 KΩ. This large resistancevariability imposes a challenge on the design of the resistancemeasurement circuitry. In addition, the ratio of the change inresistance to the initial baseline resistance, or ΔR/R, which isindicative of the concentration of the analytes, can be very small(i.e., on the order of hundreds of parts per million, or 0.01%). Thissmall amount of change, likewise, imposes a challenge on the design ofthe measurement circuitry. Further, some sensor module embodimentsinclude multiple (e.g., 32) chemically sensitive resistors, and it isdesirable to measure the resistance values of all resistors with minimumcircuit complexity.

FIG. 12B shows an embodiment of a voltage divider network used tomeasure the resistance of a chemically sensitive resistor 1220.Chemically sensitive resistor (Rch) 1220 is coupled in series to areference resistor (Rref) 1222 to form a voltage divider network. In anembodiment, a number of voltage divider networks are formed, one networkfor each chemically sensitive resistor, with each network including achemically sensitive resistor coupled in series to a correspondingreference resistor. The reference resistors are selected to have arelatively low temperature coefficient. In an alternative embodiment, asingle reference resistor is coupled to all chemically sensitiveresistors.

Referring back to FIG. 12A, a power supply 1224 supplies a predeterminedreference voltage (Vref) to the voltage divider networks such that smallchanges in the resistance value of each chemically sensitive resistorcause detectable changes in the network output voltage. By appropriatelyselecting the values of the reference resistors, the electrical currentthrough each chemically sensitive resistor can be limited, for example,to less than about 25 micro amperes (μA). This small amount of currentreduces the amount of 1/f noise and improves performance.

The analog voltages from the resistor divider networks are providedthrough a multiplexer (MUX 1226 to an analog-to-digital converter (ADC)1230. MUX 1226 selects, in sequence, the chemically sensitive resistorson the sensor module. Optionally, a low-noise instrumentation amplifier1228 can be used to amplify the voltage prior to digitization, toimprove the ADC's performance and provide increased resolution.

In an embodiment, ADC 1230 is a 22-bit (or higher) delta-sigma ADChaving a wide dynamic range. This allows low-noise amplifier 1228 to beset to a fixed gain (i.e., using a single high precision resistor).Commercially available low cost delta-sigma ADCs can reach samplingspeeds as fast as about 1 millisecond per channel.

In one implementation, the reference voltage provided by power supply1224 to the voltage divider networks is also provided to a referenceinput of ADC 1230. Internally, ADC 1230 compares the divider networkoutput voltages to this reference voltage and generates digitizedsamples. With this scheme, adverse effects on the divider network outputvoltages due to variations in the reference voltage are substantiallyreduced.

The digitized samples from ADC 1230 are provided to processor 1210 forfurther processing. Processor 1210 also provides timing signals to MUX1226 and ADC 1230. Timing for the data acquisition can also be providedvia a serial link to the ADC and via select lines of the MUX.

FIG. 12C is a diagram of another embodiment of the electrical circuitrywithin e-nose device 100. In FIG. 12C, four 8-channel multiplexers(MUXes) 1256 a through 1256 d are provided for added flexibility. Theinputs of MUXes 1256 couple to the voltage divider networks (not shown)and the outputs of MUXes 1256 a through 1256 b couple to four amplifiers1258 a through 1258 d, respectively. The select lines for MUXes 1256 areprocessor controlled. The use of external MUXes offer a low ONresistance and fast switching times. The outputs of amplifiers 1258couple to four inputs of an ADC 1260.

Each amplifier 1258 is a differential amplifier having a reference(i.e., inverting) input that couples to a digital-to-analog converter(DAC) 1262. The DC offset of the amplifier is controlled by processor1250 by measuring the offset with ADC 1260 and directing DAC 1262 toprovide a proper offset correction voltage. To account for DC-drift(i.e., drift in the baseline resistance of the chemically sensitiveresistor) the offset can be adjusted prior to actual measurement.Further electrical stability is maintained by placing ADC 1260 on-boardand using differential MUXes.

In the embodiments in FIGS. 12A and 12C, amplification is used with thevoltage divider networks to achieve detection of PPM changes inresistance values. It can be shown that a gain of 50 provides detectionof single PPM increments. In FIG. 12C, amplifiers 1258 also match thesignal to be sampled with the full-scale input of ADC 1260. Thismatching is accomplished by subtracting out the DC component (using DAC1262) and amplifying the AC component. Thus, it is possible to detectsingle PPM changes even with a baseline resistance that varies by ±50%.

In FIGS. 12A and 12C, the ADCs used to measure the resistance values canbe implemented using a (i.e., 4-channel) high-resolution delta-sigmaADC. The delta-sigma ADC's high resolution coupled with theabove-described sensor biasing scheme(s) deliver high flexibility andprecision. Presently available delta-sigma ADC can provide 20 bits ormore of effective resolution at 10 Hz and 16 bits of resolution at 1000Hz, with power consumption as low as 1.4 mW.

In an embodiment, the delta-sigma ADC includes differential inputs,programmable amplifiers, on-chip calibration, and serial peripheralinterface (SPI) compatibility. In an embodiment, the ADC internaldifferential MUXes are configured: (1) with respect to ground forincreased effective resolution of the measurement, and (2) configuredwith respect to the reference voltage for high precision measurement,enhanced electronic stability, and to provide a ratiometric measuringmechanism. A status signal from the ADC indicates when the internaldigital filter has settled, thus providing an indication to select thenext analog channel for digitization.

In FIGS. 12A and 12C, processors 1210 and 1260 can be implemented as anapplication specific integrated circuit (ASIC), a digital signalprocessor (DSP), a controller, a microprocessor, or other circuitsdesigned to perform the functions described herein.

One or more memory devices are provided to store program codes, data,and other configuration information, and are mounted adjacent to theprocessor. Suitable memory devices include a random-access memory (RAM),a dynamic RAM (DRAM), a FLASH memory, a read only memory (ROM), aprogrammable read only memory (PROM), an electrically programmable ROM(EPROM), an electrically erasable and programmable PROM (EEPROM), andother memory technologies. The size of the memories is applicationdependent, and can be readily expanded as needed.

In an embodiment, the processor executes program codes that coordinatevarious operations of the e-nose device. The program codes includeinteraction software that assists the user in selecting the operatingmodes and methods and to initiate the tests. After the e-nose deviceperforms a test or operation, the user is optionally presented withconcise results. In the embodiment in which the device includes aprocessor and a built-in algorithm, complex functions and capabilitiescan be provided by the device. In other embodiments in which simplifiedelectronics is provided, complex functions and capabilities of thee-nose device are optionally set up and driven from a host computerusing PC based software.

The processors can also be used to provide temperature control for eachindividual sensor array device in the sensor module. In animplementation, each sensor array device can include a back-side heater.Further, the processor can control the temperature of the samplechambers (e.g., chambers 710 a and 710 b in FIG. 7A) either by heatingor cooling using a suitable thermoelectric device (not shown).

After the processor has collected data representing a set of variableresistance measurements for a particular unknown test sample, itproceeds to correlate that data with data representing a set ofpreviously collected standards stored in memory (i.e., either RAM 1212or ROM 1214). This comparison facilitates identification of analytespresent in the sample chamber and determination of the quantity orconcentration of such analytes, as well as detection of temporal changesin such identities and quantities. Various analyses suitable foridentifying analytes and quantifying concentration include principalcomponent analysis, Fischer linear analysis, neural networks, geneticalgorithms, fuzzy logic, pattern recognition, and other algorithms.After analysis is completed, the resulting information is displayed ondisplay 120 or transmitted to a host computer via interface 1232, orboth.

The identification of analytes and the determination of sampleconcentration can be performed by an “analyzer.” As used herein, theanalyzer can be a processor (such as processors 1210 and 1260 describedabove), a DSP processor, a specially designed ASIC, or other circuitsdesigned to performed the analysis functions described herein. Theanalyzer can also be a general-purpose processor executing program codeswritten to perform the required analysis functions.

As noted above, to facilitate identification of specified analytes, thevariable resistance data from the sensors for a particular unknown testsample can be correlated with a set of previously collected standardsstored in memory. These standards can be collected using one of at leasttwo suitable techniques, as described below.

In one technique, a known reference sample is provided to the samplechamber(s). The known sample can be supplied from a small referencecartridge (i.e., located within the e-nose device). The supplies of thisreference sample to the sample chambers can be controlled by a compactsolenoid valve under the control of the processor. An advantage of usinga known reference sample is the ability to control the identity of thereference sample. The cartridge can be replaced periodically.

In another technique, the unknown test sample supplied to the samplechambers can be selectively “scrubbed” by diverting it through acleansing agent (e.g., charcoal). Again, the diversion of the testsample through the cleansing agent can be controlled by the processorvia a compact solenoid valve. An advantage of this variation is that acartridge is not needed. The cleansing agent can be cleanedperiodically, although it may be difficult to ensure that the referencesample is free of all contaminants.

The processors in FIGS. 12A and 12C direct data acquisition, performdigital signal processing, and provide control over serial peripheraldevices (via SPI), I/O devices, serial communications (via SCI), andother peripheral devices. Serial peripheral devices that can becontrolled by the processors include the ADC and DAC, a 32K externalEPROM (with the capability to expand to 64K), a 32K RAM with integratedreal time clock and battery back up, a 2×8-character dot matrix display,and others. I/Os that can be controlled include five separatetemperature probes (four are amplified through amplifiers and are usedfor four independent heater control loops utilizing transistors), ahumidity probe, two push buttons, a green LED, and others. Serialcommunications to external devices is provided by the on-board low powerRS-232 serial driver.

The processors further control the peripheral devices such as thedisplay, the valve assembly, and the pump. The processors also monitorthe input devices (e.g., push button switches 122 in FIG. 2A) andfurther provides digital communication to a host computer via aninterface (e.g., the RS-232 driver) located in the device's housing(e.g., electrical connector 126 in FIG. 2A).

In the embodiment in FIG. 12C, data acquisition includes communicationand/or control over the (i.e., 20 bit) delta-sigma ADC, the 4-channel(i.e., 12-bit) DAC 1262, and the four discrete 8-channel high-speedanalog MUXes 1256.

The on-board memory (i.e., external RAM) is provided for data loggingpurposes. In an embodiment, the memory is organized in blocks of 32K×8bits. In an embodiment, each sample from the ADC is 24 bits and occupiesthree bytes of memory. Thus, each 32K-byte memory block provides storagefor 10,666 samples. If all 32 channels are used for data loggingpurposes, the memory block provides storage for 333 data points/channel.An internal power supply preserves the data stored in the memory and isdesigned with a lifetime of over five years. The ADC sampling rate isprogrammable and the data can be downloaded over the digital RS-232interface to the host computer.

Communication between the on-board processor and the host computer isavailable to configure the device and to download data, in real time orat a later time via the RS-232 interface. A transfer rate of 9600bits/second can transmit approximately 400 data points/second, andhigher transfer rates can be used.

FIGS. 13A through 13G depict an embodiment of suitable flowcharts of thefunctional steps performed by the e-nose device in implementing themeasurement and analysis procedures outlined generally above. Theseflowcharts show how the e-nose device is initialized and then controlledthrough its various operating modes. In an embodiment, these operatingmodes include: 1) a Target mode, in which the device is calibrated byexposing it to samples of known identity, 2) an Identify mode, in whichthe device is exposed to a samples of unknown identity, and 3) a Purgemode, in which the device is purged of resident samples.

FIG. 13A shows a flow diagram of an embodiment of the main program menuof the e-nose device. Initially, the e-nose device's various electronicelements (i.e., the display and various internal data registers) areinitialized or reset, at a step 1312. A function background subroutineis then executed, at a step 1314. This subroutine is further describedin FIG. 13B.

After executing the function background subroutine, the program proceedsto a step 1316 in which the processor determines whether or notpush-button switch B1 (e.g., switch 122 a in FIG. 2A) is being pressed.If it is, the program proceeds to a step 1318 in which the device'soperating mode increments to the next succeeding mode (i.e., from theTarget mode to the Identify mode). Thereafter, the program returns tostep 1314 and re-executes the function background subroutine. Theincrementing of the device's operating mode continues until it isdetermined in step 1316 that switch B1 is no longer being pressed.

If it is determined at step 1316 that push button B1 is not (or nolonger) being pressed, the program proceeds to a step 1320 in which itis determined whether or not push-button switch B2 (e.g., switch 122 bin FIG. 2A) is being pressed. If switch B2 is not being pressed, theprogram returns via an idle loop 1322 to step 1314 and re-executes thefunction background subroutine. Otherwise, if it is determined at step1320 that push-button switch B2 is being pressed, the program proceedsto implement the selected operating mode. This is accomplished by theflowchart depicted in FIG. 13C. FIG. 13B shows a flow diagram of anembodiment of the function background subroutine (step 1314). At a step1330, signals indicative of the measurements and parameters selected bythe user (i.e., the temperature and humidity within the sample chambersof the sensor module) are read from the ADCs configured to detect theinput devices (also referred to as the internal ADCs). The status of thepush-button switches (e.g., switches 122 a through 122 c FIG. 2A) aredetermined, at a step 1332, based on the signals from the internal ADCs.The signals controlling the heaters located on various sensor arraydevices of the sensor module are then updated, at a step 1334. Signalsindicative of the measurements of the divider networks, formed by thechemically sensitive resistors and their corresponding referenceresistors, are read from the instrumentation ADCs (also referred to asthe external ADCs), at a step 1336. Finally, at a step 1338, theprocessor processes any commands received from the host computer via theserial data line. Such commands can include, for example, programminginformation about the identity of various reference samples to besupplied to the e-nose device during the target operating mode. Thefunction background subroutine then terminates.

FIG. 13C shows a flow diagram of an embodiment of a subroutine fordetermining which one of the operating modes to implement. At a step1340, a determination is made whether or not the selected operating modeis the Target mode. If it is not, a determination is made whether or notthe selected operating mode is the Identify mode, at a step 1342.Typically, the Identify mode is selected only after the target modesubroutine has been implemented for all of the designated targetsamples. If the selected operating mode is the Identify mode, theprogram executes the identify mode subroutine (depicted in FIG. 13E), ata step 1344.

Otherwise, if the selected operating mode is not the Identify mode, adetermination is made whether or not the selected operating mode is thePurge mode, at a step 1346. If it is, the program executes the purgemode subroutine (depicted in FIG. 13F), at a step 1348. Otherwise, theprogram executes the purge target mode subroutine (depicted in FIG.13G), at a step 1350. The purge target mode is the default mode.

Back at step 1340, if it is determined that the selected operating modeis the Target mode, the program proceeds to a step 1352 in which thefunction background subroutine is executed. This provides updated valuesfor the internal and external ADCs, as described above. Thereafter, at astep 1354, it is determined whether or not push-button switches B1 andB2 are being pressed concurrently. If they are, the program does notimplement the Target mode and instead returns to the idle loop (step1322 in FIG. 13A).

Otherwise, if it is determined at step 1354 that both push-buttonswitches B1 and B2 are not being pressed concurrently, the programproceeds to a step 1356 in which it is determined whether or not switchB1 has been pressed. If it has been, the program proceeds to a step 1358in which the particular target number is incremented. In an embodiment,the e-nose device is configured to measure multiple (e.g., eight)different target samples, and step 1358 enables the operator to selectthe particular target sample that is to be drawn into the device formeasurement. The identity of these target samples previously has beenloaded into the device from the host computer. Thereafter, the programreturns to the step 1352 to execute the function background subroutine.Each time it is determined that switch B1 has been pressed, the programcycles through this loop, incrementing through the preloaded complementof target samples.

If it is determined at step 1356 that switch B1 has not been pressed,the program proceeds to a step 1360 in which it is determined whether ornot switch B2 has been pressed. If it has not, the program returns tostep 1352 to execute the function background subroutine. Otherwise, ifit is determined in step 1360 that switch B2 has just been pressed, theprogram proceeds to implement the target mode subroutine (depicted inFIG. 13D), at a step 1362.

FIG. 13D shows a flow diagram of an embodiment of the target modesubroutine. At a step 1370, the most recently updated set ofmeasurements from the external ADC is retrieved. These measurementsrepresent the baseline resistance values of the 32 chemically sensitiveresistors of the sensor module. Next, the pump is conditioned to drawthe designated target sample into the sensor module's sample chamber(s),at a step 1372. A new set of measurements is then retrieved from theexternal ADC, at a step 1374. This new set of measurements indicates theresistance values of the 32 chemically sensitive resistors as theyrespond to the target sample that has been drawn in the samplechamber(s).

At a step 1376, the 32 resistance measurements (i.e., the “responsevector”) for this particular target vapor are normalized. In anembodiment, this normalization set the sum of all 32 measurements equalto a value of 1×10⁶. The normalized response vector for this targetsample then is stored in memory, at a step 1378. Finally, at a step1380, the pump and valve assembly are configured to draw clean air intothe sample chamber(s). The target mode subroutine then terminates, andthe program returns to the idle loop (step 1322 in FIG. 13A).

FIG. 13E shows a flow diagram of an embodiment of the identify modesubroutine. Steps 1390, 1392, 1394, and 1396 in FIG. 13E are similar tosteps 1370, 1372, 1374, and 1376 in FIG. 13D, respectively. At a step1398, the normalized response vector for the unknown sample calculatedin step 1396 is compared with the normalize response vectors for thevarious target samples, as determined by earlier passes through thetarget mode subroutine (FIG. 13D) and stored in memory. Specifically,differences between the respective normalized response vectors arecalculated at step 1398, and the smallest difference vector isdetermined (i.e., using a least mean square analysis), at a step 13100.Also at step 13100, the result of that determination is displayed on adisplay. Finally, at a step 13102, the pump and valve assembly areconditioned to draw clean air to the sample chamber(s). The identifymode subroutine then terminates, and the program returns to the idleloop (step 1322 in FIG. 13A).

FIG. 13F shows a flow diagram of an embodiment of the purge modesubroutine. At a step 13120, the pump and valve assembly are conditionedto draw clean air into the sample chamber(s) via the intake port. Theprogram then returns to the idle loop (step 1322 of FIG. 13A).

FIG. 13G shows a flow diagram of an embodiment of the purge target modesubroutine. At a step 13130, all of the target sample information storedin memory is erased. The program then returns to the idle loop (step1322 in FIG. 13A).

FIG. 14 shows a diagram of an embodiment of the menu selection for thee-nose device. In FIG. 14, a main menu 1408 displays the measurementmodes available for the particular e-nose device. The available modescan be dependent, for example, on the particular modules installed inthe e-nose device. In an embodiment, the following modes are availablein the main menu: Identify, Quantify (Qu), Process Control (PC), DataLogging (DL), Train, and Diagnoses. Upon making a mode selection in menuscreen 1408, a menu screen 1410 appears that queries the user to selecta particular method from among a set of available methods.

By selecting the ID Method option, a menu screen 1412 appears thatqueries the user to press “sniff” to begin identification or “cancel” toreturn to the main menu. Upon selecting the sniff option, the e-nosedevice begins the identification process, as shown in a menu screen1414, and provides the results upon completion of the process, as shownin a menu screen 1416. The user is provided with an option to save theresults.

By selecting the Qu Method option, a menu screen 1420 appears thatqueries the user to select a target. If the identity of the target isunknown, a menu screen 1422 provides the user with the option ofperforming a sniff to identify the unknown target. Upon selecting thesniff option, the e-nose device begins the identification process, asshown in a menu screen 1424, and provides the identity upon completionof the process, as shown in a menu screen 1426. Once the sample isidentified or if the identity is known initially, the target can bequantified in menu screens 1426 and 1428. The e-nose device begins thequantification process, as shown in a menu screen 1430, and provides theresults upon completion of the process, as shown in a menu screen 1432.

By selecting the PC Method option, a menu screen 1440 appears thatqueries the user to press “sniff” to begin the process control or“cancel” to return to the main menu. Upon selecting the sniff option,the e-nose device begins the process control, as shown in a menu screen1442, and provides the status report, as shown in a menu screen 1444.

By selecting the DL Method option, a menu screen 1450 appears thatqueries the user to press “sniff” to begin the data logging or “cancel”to return to the main menu. Upon selecting the sniff option, the e-nosedevice begins the data logging process, as shown in a menu screen 1452,and provides the status report, as shown in a menu screen 1454.

By selecting the Train option, a menu screen 1460 appears that queriesthe user to select one of a number of training methods. The user selectsa particular method and a menu screen 1462 appears that queries the userto select one of a number of targets. The user selects a particulartarget and a menu screen 1464 appears that queries the user to press“sniff” to begin the training. Upon selecting the sniff option, thee-nose device begins the training process using the method and targetselected by the user, as shown in a menu screen 1466.

By selecting the Diagnostics option, a menu screen 1470 appears thatqueries the user to select a diagnostic to run. Possible diagnosticsinclude, for example, RS-232 port, USB port, sensor range test, memory,processor, and program check sum. The user selects a particulardiagnostic and the e-nose device begins the selected diagnostic test, asshown in a menu screen 1472, and provides the diagnostic results, asshown in a menu screen 1474.

Modular Design

In certain aspects of the invention, the e-nose device is designed usingmodular sections. For example, the nose, filter, manifold, sensormodule, power pack, processor, memory, and others can optionally bedisposed within a module that can be installed or swapped, as necessary.The modular design provides many advantages, some of which are relatedto the following characteristics: exchangeable, removable, replaceable,upgradable, and non-static.

With a modular design, the e-nose device can be designed for use in widevariety of applications in various industries. For example, multiplesensor modules, filters, and so on, can be added as the list of samplesto be measured expands.

In certain embodiments, the modular design can also provide improvedperformance. The various modules (i.e., nose, filter, manifold, sensormodule, and so on) can be designed to provide accurate measurement of aparticular set of test samples. Different modules can be used to measuredifferent samples. Thus, performance is not sacrificed by the use of asmall portable e-nose device. For example, to sense high molecularweight analytes, a certain particular nose chip is plugged in. Then, toanalyze lower molecular weight analytes, another nose chip may beplugged in.

The modular design can also result in a cost effective e-nose design.Since some of the components can be easily replace, it is no longernecessary to dispose the entire e-nose device if a particular componentwears out. Only the failed components are replaced.

In certain embodiments, the modular design can also provide anupgradable design. For example, the processor and memory module(individually or in combination) can be disposed within an electronicunit that can be upgraded with new technologies, or as required by onthe particular application. Additional memory can be provided to storemore data, by simply swapping out memory modules. Also, the analysisalgorithms can be included in a program module that inserts into thee-nose device. The program modules can then be swapped as desired.

The modular design can also provide for disposable modules. This may beadvantageous, for example, when analyzing toxic samples.

Nose

In the embodiments described above, the e-nose device includes anexternal sampling wand (or nose or snout). The nose can be attached tothe device using a mechanical interconnect, such as a simple ¼-turntype, a threaded screw, a snap-on mechanical arrangement, and otherinterconnect mechanisms. Many materials can be used to fabricate thenose component, such as injection moldable materials.

In certain embodiments, the nose is interchangeable and uses a standardluer interconnection. The nose can be, for example, about 1 inch toabout 50 inches in length and, preferably, the nose is about 6 inches toabout 20 inches in length. The nose can optionally be ridged, or be along flexi-hose or a flexible snorkel. In some embodiments, the nose hasa luer needle on the smelling end. Optionally, the nose can withstand aninternalized pressure and is joined with a pressured valve.

As shown in FIG. 3B, the nose can be dimensioned in various sizes andshapes. For example, nose 130 d includes a wide opening that may beadvantageous, for example, when sampling a gas. In contrast, nose 130 fincludes a pointed tip that is more suited for sampling at a specificsite.

In some alternative embodiments, intake ports (such as intake port 132)can be used to receive test samples. The intake ports can substitutefor, or supplement the external nose.

Sensor Modules

In certain aspects, the chemically sensitive sensors in the sensormodule can be tailored to be particularly sensitive to particularclasses of vapors. For example, the array for one such module canincorporate vapor sensors suitable for differentiating polar analytessuch as water, alcohol, and ketones. Examples of polar polymers suitablefor use as such vapor sensors include poly (4-vinyl phenol) and poly(4-vinyl pyrrolidone).

The sensor module can optionally be identified by means of anidentification resistor (not shown) having a selected resistance. Thus,prior to processing the variable resistance measurements collected forthe chemically sensitive resistors of each such sensor module, theprocessor measures the resistance of the identification resistor. Inthis manner, the nature of the module's chemically sensitive resistorscan be initially ascertained.

A mechanism for detection of analytes is disclosed in the aforementionedPCT Patent Application Serial No. WO99/08105.

Display

In some embodiments, the display is a liquid-crystal display (LCD). Inother embodiments, the display is a graphical LCD that allows the deviceto display text and graphics. This type of display provides a qualityproduct interaction experience. Examples of LCD modules include thosemanufactured by Epson Corporation, such as the EPSON EG7502 (TCM AO822)having a screen size of 57.56 mm by 35.99 mm, a 320×200 resolution with0.8 dot pitch, and transflective and LED edge back light. Various otherLCD modules are also suitable. Preferred LCD modules offer one or moreof the following features: (1) higher resolution to allow for a smallerbut comfortable display viewing areas (320×200 and fine dot pitch), (2)low power consumption (e.g., 3 mW to 9 mW), (3) multi-linescanning-(active addressing) technology, (4) integrated “touch” panel,(5) integrated power supply and controller chips, (6) LEDbacklighting—for smaller module, (6) displays used with video, and otherfeatures.

Input Devices

In certain embodiments, the e-nose device optionally includes inputdevices, such as push buttons, a keypad, a keyboard, a touchscreen,switches, other input mechanisms, or a combination of the above. Thekeypad can be fabricated from various materials. In certain embodiments,the keypad is molded from silicone rubber, which advantageously providestactile feedback for gloved hands. Moreover, navigational controls canoptionally be incorporated into the keypad and buttons. For example, a“sniff” button can be optionally positioned into the keypad.

The keypad can optionally be a membrane type keypad. In thisimplementation, the keypad is formed from laminated sheets of acrylic,Mylar, PC, or other suitable materials. Snap domes can be used toachieve greater tactile feedback for the user. Product graphics can beincorporated into the keypad. Advantageously, the keypad has flexibilitywith graphics, is easy to clean, and has protection from spillage. Inaddition, the keypad is configured with low stroke distances. In certainother instances, a micro-switch, such as for a “sniff” button, is usedto further accentuate the tactile “click” feedback and generate alow-level audible signal.

In certain embodiments, the e-nose device optionally includes a pointer.Advantageously, the pointer provides greater application flexibility andease of use in the field. In certain aspects, the pointer can be usedfor bar code reading and easy inventory control. Further, the deviceoptionally includes a pad. The pad allows for application flexibility,such as in field, training, or lab use.

The e-nose device optionally includes other input devices, such as atouch screen. Suitable touch screens include the analog resistive type.Other touch screens include those similar to the ones in PDA, GPS, andother products. Yet other touch screens include electromagneticresonance types optionally having a dedicated stylus, such as abattery-less stylus. In addition, touch screens can include, but are notlimited to, electrostatic, GSAW, and analog resistive and capacitivetypes. The analog resistive touch screen is preferred since high and lowresolutions can readily be achieved.

In certain embodiments, the e-nose device notifies the user by providinggeneral and specific information about the device's current mode.Operators of the device can see what options are available. Guidelinesand instructions are available to assist the users interact with theproduct. In certain instances, the descriptions and instructions arebrief and specific. Graphics and icons assist users through the productinteraction. Users are provided with a mechanism to stop the device whennecessary, and to return to previous screens where appropriate. Thesevarious features collaborate to provide device interactions that arequick, simple, and reliable.

In other embodiments, the e-nose device provides the users withinformation regarding the status of the device. Examples include, butare not limited to, initiating an action, performing an operation,waiting for input, and so on. Moreover, other device input and outputparameters, such as hardware controls, include, but are not limited to:Scroll Up—keypad; (2) Scroll Down—keypad; (3) Select—keypad; (4)Cancel—keypad; (5) Sniff—keypad; (6) Power-on/Backlight on/off; (7)Digital Input—connector, (8) Analog Output—connector; (9) Serial out(RS232)—RJ11; (10) USB—Standard A; (11) Display contrast—(thumbwheel,analog pot); (12) System reset—pinhole; (13) Battery recharge—jack; (14)pneumatics ports; (15) nose inhale port (sample sniff port); (16) exhale(exhaust); and (17) reference intake.

Power Pack

The e-nose device optionally includes a power pack, such as a battery,for providing electrical power. In certain embodiments, the deviceoperates from power supply voltages of approximately 3.3 volts andapproximately 5.0 volts DC. In a specific embodiment, the deviceconsumes approximately 3.2 watts or less, with a typical average powerconsumption of approximately 1.8 watts. In an embodiment, the device iscapable of operation from about 1 hour to about 20 hours withoutrequiring a recharge of the power pack.

The power pack can be fabricated using nickel cadmium (NiCd),nickel-metal hydride (NiMH), lithium ion (Li-ion), sealed lead-acid(SLA), or other battery technologies. Preferably, the battery pack haslow weight and a high power density to keep the volume of the batterysmall. Lithium-ion cells have a relatively high internal resistance andwider range of voltages during a discharge compared to other batterychemistries. A voltage regulator can be used to provide proper voltagesfor the circuitry within the e-nose device. For efficiency, a switchingvoltage regulator can be used in place of linear type regulators. Thevoltage regulator can also be used to provide multiple output voltagesfor different circuitry within the e-nose device. In certain instances,output voltages required from the power supply include values above andbelow the battery voltage. In these instances, a SEPIC topology for theswitching regulator can optionally be used. Conversion efficiency ofsuch switching regulators is approximately 85%. To provide approximately18 watt-hours of energy to the load using such switching regulator, theenergy requirement from the lithium-ion battery pack is approximately 21watt-hours.

In a specific embodiment, a lithium-ion (Li-ion) battery pack ofapproximately 100 cubic centimeters (cc) in volume and about 250 gramsin weight can optionally be used for the e-nose device. In anotherspecific embodiment, a nickel-metal hydride (NiMH) battery pack can beused that weighs about 370 grams and has a volume of about 150 cc. Otherbatteries capable of providing an equivalent amount of energy include,but are not limited to, a nickel-cadmium (NiCd) battery pack ofapproximately 560 grams and 210 cc and a sealed lead-acid (SLA) batterypack of approximately 750 grams and 350 cc.

In general, charging times increase and the available battery capacityreduces for low (e.g., 0 to 10° C.) and high (e.g., 40 to 50° C.)temperatures. For accurate “gas gauging” under such conditions, theSmart Battery System (SBS) can also be employed. The SBS is part of acommercially available System Management Bus (SMB) system. The SBSallows battery packs to communicate to smart chargers and other systemintelligence using a physical protocol similar to the I²C bus protocolfrom Philips Corporation. The software protocol on the SMB allows fordirect communication of parameters such as the state of charge, batterypack voltage, battery temperature, number of discharge cycles, and soon. Several vendors of integrated circuits now offer single chipimplementations of the SMB interface. Alternatively, a custom programmedmicrocontroller, such as a PIC chip Microchip Technology Inc., can beused for this purpose.

In some embodiments, the device includes a power pack that is optionallychargeable. In some other embodiments, the device optionally includesbatteries such as, for example, four AA cells. The cell chemistries canvary. The device optionally accommodates alkaline interchangeability.

The device optionally has a fitting for a secondary rechargeable packthat can be the same, or smaller, size as the power devices describedabove.

Specific Electronic-Nose Device Implementations

The e-nose device can be implemented in various configurations, toinclude various features, and be used in various applications. Somespecific implementations are provided below.

In one specific implementation, the e-nose device includes a sensorarray of 32 sensors, composed of conducting particles uniformlydispersed in a polymer matrix. Each polymer expands like a sponge whenexposed to a test medium (e.g., vapor, liquid, gas), thereby increasingthe resistance of the composite. The polymers expands to varying degreesbecause of their unique response to different analytes. This change inresistance varies across the sensor array, producing a distinctivesignature response. Regardless of whether the analytes correspond to acomplex mixture of chemicals in the test sample or from a singlechemical, the e-nose device includes sufficient polymer arrays toproduce a distinct electrical “fingerprint” for the samples of interest.The pattern of resistance changes in the sensor array is indicative ofthe identity of the analytes, while the amplitude of the patternindicates the concentration of the analytes.

The normalized change in resistance is then transmitted to a processorthat identifies the type, quantity, and quality of the vapor based onthe detected pattern in the sensor array.

In another specific implementation, a portable e-nose device for use inthe field to detect volatile compounds is fabricated according to theinvention. The device incorporates an easy-to-read graphic LCD with backlighting and one or more light emitting diodes (LEDs) to indicate modeof operation. Communications ports are provided to enable easydownloading of data into a spreadsheet package. Rapid response time,combined with easy one-button operation, provide an effective andaccurate measurement of the samples. Power is supplied by replaceable orrechargeable batteries. Housed in a robust, water-resistant case, theportable e-nose device is suitable for various environments.

In yet another specific implementation, the e-nose device is designed toacquire and store data collected from 32 independent sensor elements.The e-nose device includes a 32-channel sample chamber with inlet/outletports, a pump, a 3-way solenoid switch, a LCD, push buttons, LED, ahumidity probe, a temperature probe, and a digital interface.

The power supply is designed for a 9-volt DC input. A rectifying diodeis added for circuit protection. Two on-board 5-volt linear regulatorsare utilized for the analog and digital circuitry, respectively. A highprecision buried Zener diode is provided to supply a +2.5 voltreference. The overall design is a mixed 3V and 5V design for reducedpower consumption in a handheld device.

The sample chamber houses 32 sensor elements deposited on four ceramicsubstrates, each with eight sensor elements. The substrates arefabricated using hybrid microelectronic co-fired ceramic (alumina)processes. Electrodes and contacts are deposited as thick films usingscreen-printing techniques. Resistive paths can be provided (e.g., threepaths) to be used as heating elements. On the backside of the substrate,a surface mount thermistor can be placed to form a heating/coolingcontrol loop.

An inlet port is provided and a baffle can be inserted to fan out theincoming sample stream. The outlet port is respective to ambientbarometric pressures. The sample chamber can be fabricated of Teflon andis airtight, and is mount to the PCB. An on-board pump can push thesample flow into the sample chamber at pressures slightly higher than14.7 psi. The on-board 3-way solenoid switch can switch under processorcontrol between a known reference source (i.e., to “re-zero” orrecalibrate as necessary) and an unknown test sample. The four ceramicsubstrates are inserted in two 20-pin, 50-mil spacing, dual rowconnectors. The spacing between the rows is 100 mils. A temperatureprobe is inserted into one connector and a humidity probe is insertedinto the other. The temperature and humidity probes are used fordiagnostics.

A biasing network can been implemented that biases the chemicallysensitive resistor in a DC mode of operation. The network is aratiometric network that is easy to implement and stable, and offers awide dynamic range.

It has been shown that 50 PPM changes in electrical resistance of thechemically sensitive can be measured. Further, baseline changes greaterthan ±50% can be accounted for with minimal change in applied power, asshown in Table 1.

TABLE 1 Detectable Changes in Resistance for Various BaselineResistances Baseline Vout Applied Power Resolution 15K (−Δ50%) 0.3260.047 18 bits 20K (−Δ33%) 0.417 0.043 18 bits 25K (−Δ17%) 0.500 0.040 17bits 30K, nominal 0.577 0.037 17 bits resistance 35K (+Δ17%) 0.648 0.03417 bits 40K (+Δ33%) 0.714 0.032 17 bits 45K (+50%) 0.776 0.030 17 bits

Assuming that Johnson noise is the dominant noise source, it is possibleto calculate an average noise voltage of 0.3 μV over a 10 Hz bandwidthand can thus detect these step changes. By keeping the current low(i.e., <25 μA) the 1/f noise is reduced. In general, the biasing schemeis a constant voltage, DC system. The current is limited tomicro-amperes (μAs) per sensor element and the applied power is in theorder of micro-watts (μWs). For added flexibility the current is limitedand the output voltage is scaled by resistors.

The handheld sensing apparatus of the present invention was used tosense a series of four (4) homologous ester analytes. The analytessensed were the ethyl esters of propionate, butyrate, valerate, andhexanoate. The response data was then analyzed using principal componentanalysis. Principal Component Analysis (PCA) is a powerful visualizationtool that provides a way to reduce the dimensionality of the data. PCAfinds linear combinations of the original independent variables thataccount for maximal amounts of variation and provides the best possibleview of variability in the independent variable block. Naturalclustering in the data is readily determined.

FIG. 15 shows a graph of a principal component analysis of the responsesto a series of esters using the handheld apparatus of the presentinvention. As shown in FIG. 15, the ester analytes were welldiscriminated by the handheld device of the present invention.

Analytes and Applications of the E-Nose Device

Analytes detectable by the e-nose device of the invention include, butare not limited to, alkanes, alkenes, alkynes, dienes, alicyclichydrocarbons, arenes, alcohols, ethers, ketones, aldehydes, carbonyls,carbanions, heterocycles, polynuclear aromatics, organic derivatives,biomolecules, microorganisms, bacteria, viruses, sugars, nucleic acids,isoprenes, isoprenoids, and fatty acids and their derivatives. Manybiomolecules, such as amino acids, are amenable to detection using thesensor arrays of the invention.

The e-nose device can be used to enable medical and dentalcare-providers to quickly and accurately identify the chemicalcomponents in breath, wounds, and bodily fluids to diagnose a host ofillness including infections and metabolic problems. For example, thee-nose device can be used to test for skin conditions, for anesthesiaadministration, or to determine time of ovulation in fertilitytreatment. Alternatively, the handheld device can classify and identifymicroorganisms, such as bacteria.

The e-nose device can be used to locate an odor to identify acomplicated system or state of matter, and can offer versatility andreliability absent from conventional environmental or chemicalmonitoring devices. Advantageously, the device can be used for profilinga chemical environment in a hazardous materials situation and to assistemergency crews to accurately select fire retardant, containmentstrategies, and protective gear.

The e-nose device can be used to detect leaks in pipelines and storagecontainers.

The e-nose device can be used in food quality and processing control.For example, the device can be used to spot test for immediate resultsor to continually monitor batch-to-batch consistency and spoilage invarious stages of a product, including production (i.e., growing),preparation, and distribution. The device can also be used in disposablepackaging to providing an objectivity that is absent from conventionalspoilage, freshness, and contamination monitoring techniques.

The e-nose device can also be used in protecting the elderly, who tendto lose sense of smell over time. The device can be used to reduce therisk of food poisoning or the ingestion of spoiled food, and can beintegrated with household appliances, such as refrigerators andmicrowave ovens.

The e-nose device can be used in a wide variety of commercialapplications including, but not limited to:

applications such as utility and power, oil/gas petrochemical,chemical/plastics, automatic ventilation control (cooking, smoking,etc.), heavy industrial manufacturing, environmental toxicology andremediation, biomedicine, cosmetic/perfume, pharmaceutical,transportation, emergency response and law enforcement,

detection, identification, and/or monitoring of combustible gas, naturalgas, H₂S, ambient air, emissions control, air intake, smoke, hazardousleak, hazardous spill, fugitive emission,

beverage, food, and agricultural products monitoring and control, suchas freshness detection, fruit ripening control, fermentation process,and flavor composition and identification,

detection and identification of illegal substance, explosives,transformer fault, refrigerant and fumigant, formaldehyde,diesel/gasoline/aviation fuel, hospital/medical anesthesia &sterilization gas,

telesurgery, body fluids analysis, drug discovery, infectious diseasedetection and breath applications, worker protection, arsoninvestigation, personal identification, perimeter monitoring, fragranceformulation, and

solvent recovery effectiveness, refueling operations, shipping containerinspection, enclosed space surveying, product quality testing, materialsquality control, product identification and quality testing.

It should be appreciated from the foregoing description that the presentinvention provides an improved vapor sensing instrument that not only issufficiently small and lightweight to be handheld, but also is modularso as to allow the device to be conveniently adapted for use in sensingthe presence and identity of a wide variety of specified vapors.

Although the invention has been described in detail with reference tothe presently preferred embodiments, those of ordinary skill in the artwill appreciate that various modifications can be made without departingfrom the invention. Accordingly, the invention is defined only by thefollowing claims.

What is claimed is:
 1. A handheld sensing apparatus of modular design,comprising: a housing; a plug-in sensor module including at least twosensors in at least one sampling chamber, wherein said sensors have abenefit selected from the group of being exchangeable, removeable,replaceable, upgradable and non-static, that provide a distinct responseto a particular test sample, wherein the sensor module attachesexternally to the housing; and an onboard memory module and amicroprocessor mounted in the housing and configured to analyze aparticular response from the at least two sensors in the form of anelectrical fingerprint, signature or signal, wherein the microprocessordetects, identifies or quantifies analytes within the test sample basedon the particular response.
 2. A handheld sensing apparatus of claim 1,wherein said at least two sensors are exposed to a vapor environment. 3.A handheld sensing apparatus of claim 1, wherein at least one of said atleast two sensors in said sensor module is a member selected from thegroup consisting of a conducting/nonconducting regions sensor, a SAWsensor, a quartz microbalance sensor, a conductive composite sensor, achemiresistor, a metal oxide gas sensor, an organic gas sensor, aMOSFET, a piezoelectric device, an infrared sensor, a sintered metaloxide sensor, a Pd-gate MOSFET, a metal FET structure, a electrochemicalcell, a conducting polymer sensor, a catalytic gas sensor, an organicsemiconducting gas sensor, a solid electrolyte gas sensors, and apiezoelectric quartz crystal sensor.
 4. A handheld sensing apparatus ofclaim 3, wherein at least one of the sensors in the sensor module is aconducting/nonconducting regions sensor.
 5. A handheld sensing apparatusof claim 3, wherein at least one of the sensors in the sensor module isa SAW sensor.
 6. A handheld sensing apparatus of claim 1, furthercomprising a preconcentrator.
 7. A handheld sensing apparatus of claim6, wherein said preconcentrator is externally attached to said housing.8. A method for detecting an analyte using a handheld sensing apparatushaving an array of sensors, wherein said array of sensors has a modulardesign with a benefit selected from the group of being exchangeable,removeable, replaceable, upgradable and non-static, said methodcomprising: contacting said handheld sensing apparatus with a testsample to generate a response; and analyzing said response with amicroprocessor in the form of an electrical fingerprint. signature orsignal, wherein said microprocessor detects, identifies or quantifiessaid analyte within the test sample based on said particular response byperforming digital signal processing and executing an algorithm toanalyze said response from said sensor array.
 9. The method of claim 8,wherein said array of sensors has at least one member selected from thegroup consisting of a conducting/nonconducting regions sensor, a SAWsensor, a quartz microbalance sensor, a conductive composite sensor, achemiresistor, a metal oxide gas sensor, an organic gas sensor, aMOSFET, a piezoelectric device, an infrared sensor, a sintered metaloxide sensor, a Pd-gate MOSFET, a metal FET structure, a electrochemicalcell, a conducting polymer sensor, a catalytic gas sensor, an organicsemiconducting gas sensor, a solid electrolyte gas sensors, and apiezoelectric quartz crystal sensor.
 10. The method of claim 8, furthercomprising concentrating said analyte prior to generating said response.11. A portable sensing device of modular design, comprising: a housing;a plug-in sensor module including at least two sensors with a benefitselected from the group of being exchangeable, removeable, replaceable,upgradable and non-static, that provide a distinct response to aparticular test sample; and an onboard memory module and amicroprocessor mounted in the housing and configured to analyze aparticular response from the at least two sensors in the form of anelectrical fingerprint, signature or signal, wherein the microprocessordetects, identifies or quantifies an analyte within the test samplebased on the particular response, and wherein the microprocessorperforms digital signal processing and executes an algorithm to analyzethe response from the at least two sensors.
 12. The device of claim 11,wherein said device comprises an external data port.
 13. The device ofclaim 11, wherein said device comprises a switch for controlling saidtest sample flow.
 14. The device of claim 11, wherein said devicecomprises a pump.
 15. The device of claim 14, wherein said pump is avariable speed pump.
 16. The device of claim 11, wherein said devicecomprises a temperature controlling means for controlling thetemperature of at least one of said at least two sensors.
 17. The deviceof claim 11, wherein said device comprises a means for controlling abattery charging.
 18. The device of claim 11, wherein said devicecomprises a touch pad.
 19. The device of claim 11, wherein said devicefurther comprises at least one member selected from the group consistingof a power switch, a push button, a keypad, a keyboard, a touchscreen,or a combination thereof.
 20. The device of claim 11, wherein saiddevice comprises a humidity probe.
 21. The device of claim 11, whereinsaid algorithm is a member of the group consisting of principalcomponent analysis, Fischer linear analysis, neural networks, geneticalgorithms, fuzzy logic, a least mean square analysis, and patternrecognition algorithms.
 22. The device of claim 11, wherein said atleast two sensors includes at least one member selected from the groupconsisting of a conducting/nonconducting regions sensor, a SAW sensor, aquartz microbalance sensor, a conductive composite sensor, achemiresistor, a metal oxide gas sensor, an organic gas sensor, aMOSFET, a piezoelectric device, an infrared sensor, a sintered metaloxide sensor, a Pd-gate MOSFET, a metal FET structure, a electrochemicalcell, a conducting polymer sensor, a catalytic gas sensor, an organicsemiconducting gas sensor, a solid electrolyte gas sensors, and apiezoelectric quartz crystal sensor.
 23. The device of claim 11, whereinsaid analyte is a member selected from the group consisting of anorganic molecule, a biomolecule, a fatty acid, a microorganism, abacteria, a virus, a chemical warfare agent and a toxic agent.
 24. Thedevice of claim 11, wherein said device further comprises apreconcentrator.
 25. The device of claim 22, wherein at least one ofsaid at least two sensors is a SAW sensor.
 26. The device of claim 11,wherein said device comprises a thermoelectric device.
 27. The device ofclaim 12, wherein said external port is a selected from the groupconsisting of an RS-232 port, a USB port, and combinations thereof. 28.The device of claim 11, wherein said device is configured for shippingcontainer monitoring.
 29. The device of claim 11, wherein said device isconfigured for perimeter monitoring.
 30. The device of claim 11, whereinsaid device is configured for explosive monitoring.
 31. The device ofclaim 11, wherein said device is configured for hazardous spillmonitoring.
 32. The device of claim 11, wherein said device isconfigured for communication with a host computer.
 33. The device ofclaim 11, wherein said device is configured for radiation detection.